Decompression and Fracturing Caused by Magmatically Induced Thermal Stresses

The interplay between compaction‐driven fluid flow and plastic yielding within porous media is investigated through numerical modeling. We establish a framework for understanding the dynamics of fluid flow in deforming porous materials that corresponds to the equations describing solitary porosity wave propagation. A concise derivation of the coupled fluid flow and poro‐viscoelastoplastic matrix behavior is presented, revealing a connection to Biot's equations of poroelasticity and Gassmann's theory in the elastic limit. Our findings demonstrate that fluid overpressure resulting from channelized fluid flow initiates the formation of new shear zones. Through three‐dimensional simulations, we observe that the newly formed shear zones exhibit a parabolic shape. Furthermore, plasticity exerts a significant influence on both the velocity of fluid flow and the shape of fluid channels. Importantly, our study highlights the potential of spontaneous channeling of porous fluids to trigger seismic events by activating both new and pre‐existing faults.

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Rapid Ductile Strain Localization Due To Thermal Runaway

Spang,

Thielmann,

Kiss

2024

JGR Solid Earth

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Thermal runaway is a ductile localization mechanism that has been linked to deep‐focus earthquakes and pseudotachylyte formation. In this study, we investigate the dynamics of this process using one‐dimensional, numerical models of simple shear deformation. The models employ a visco‐elastic rheology where viscous creep is accommodated with a composite rheology encompassing diffusion and dislocation creep as well as low‐temperature plasticity. To solve the nonlinear system of differential equations governing this rheology, we utilize the pseudo‐transient iterative method in combination with a viscosity regularization to avoid resolution dependencies. To determine the impact of different model parameters on the occurrence of thermal runaway, we perform a parameter sensitivity study consisting of 6,000 numerical experiments. We observe two distinct behaviors, namely a stable regime, characterized by transient shear zone formation accompanied by a moderate (100–300 K) temperature increase, and a thermal runaway regime, characterized by strong localization, rapid slip and a temperature surge of thousands of Kelvin. Nondimensional scaling analysis allows us to determine two dimensionless groups that predict the model behavior. The ratio represents the competition between heat generation from stress relaxation and heat loss due to thermal diffusion while the ratio compares the stored elastic energy to thermal energy in the system. Thermal runaway occurs if is small and is large. Our results demonstrate that thermal runaway is a viable mechanism driving fast slip events that are in line with deep‐focus earthquakes and pseudotachylyte formation at conditions resembling cores of subducting slabs.

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Decompression and Fracturing Caused by Magmatically Induced Thermal Stresses

Cited by 4 publications

References 61 publications

Seismicity near Mayotte explained by interacting magma bodies: Insights from numerical modeling

Seismicity near Mayotte explained by interacting magma bodies: Insights from numerical modeling

Shear Bands Triggered by Solitary Porosity Waves in Deforming Fluid‐Saturated Porous Media

Rapid Ductile Strain Localization Due To Thermal Runaway

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